|Location||Thramas Sector, Ultima Segmentum|
|Night Lords||Dark Angels|
| Primarch Konrad Curze(MIA)
First Captain Jago Sevatarion(POW)
Captain Var Jahan(POW)
Captain Alastor Rushal
Captain Malithos Kuln(Purged)
Captain Ithillion (KIA)
Captain Jexad (KIA)
Captain Cel Herec (Purged)
Captain Tovac Tor
| Primarch Lion El'Jonson|
Captain Alajos (KIA)
| Entire Legion
|Bulk Dark Angels Legion|
| Konrad Curze goes missing
First Captain Sevatar captured
1/5th of the Night Lords Legion
Legio Ulricon destroyed
| Moderate Dark Angels losses|
billions of civilians massacred
The Thramas Crusade was a campaign of the Horus Heresy. Waged for 3 years far from Terra in Ultima Segmentum, the Night Lords went on a rampage of terror and mayhem against worlds loyal to the Imperium.
In a bid to distract the Dark Angels from his push on Terra, Warmaster Horus despatched Konrad Curze and the Night Lords to the Eastern Fringes of the Imperium, where they undertook a campaign of terror and genocide. For nearly two years, the Dark Angels, led by their Primarch Lion El'Jonson, were bogged down in an unsuccessful campaign to stop the traitors, who utilized hit-and-run and ambush tactics, evading open battle. However eventually Konrad Curze offered a chance for parlay on the world of Tsagualsa. Bringing their Honour Guards (Corswain and Alajos of the Dark Angels and Sevatar and Sheng of the Night Lords) to the planet, the meeting between the two primarchs was very conversational, with Curze hinting that he had foreseen the Destruction of Caliban and the Fallen. The situation was peaceful until Curze slandered Lion El'Jonson and in return he struck Konrad a "dishonourable blow" and it proceeded into an all-out fight. Konrad was strangling Jonson and would have killed him had Corswain not run his sword through Konrad's spine while Alajos called for reinforcements and was then decapitated by Sevatar. Eventually reinforcements arrived for both legions and both Primarchs were dragged away from each other by their men while they were too weak to fight back. Thunderhawks then extracted the Dark Angels and both Primarchs.
After the failed meeting, the Lion was able to coordinate a masterfully executed ambush on the Night Lords fleet in the Aegis Sub-Sector thanks to his use of the recently discovered Tuchulcha engine, destroying 1/4th of the traitor armada as well as their allied Titan transport ships. Lion El'Jonson was able to meet Curze in combat once more, this time badly wounding the Night Haunter and rendering him into a comatose state. Though the Night Lords managed to escape the ambush, their Primarch was rendered comatose from his wounds and it fell to Sevatar to take command of his breaking Legion, organizing their regrouping in the second Kyroptera until Curze's recovery. Debates between Night Lords captains arose over what should be done, which resulted in Sevatar purging several rivals such as Captains Malithos Kuln and Cel Herec.
Unfortunately for the Night Lords, amid the struggle for control within their legion the Dark Angels were able to locate the bulk of their fleet and launched a renewed attack. Sevatar led a desperate counterattack that included boarding operations by the Atramentar against Dark Angels fleet. Just as the Night Lords counteroffensive was about to fail, a recovered Curze appeared once more into the fray and met the Lion aboard the Dark Angels ship Invincible Reason. After a brief duel, Curze was able to use the distraction to organize a retreat and fled the battle with his forces. However some of his warriors, Sevatar included, were left behind aboard the Dark Angels ship and captured. Curze himself was also left on the Invincible Reason, though he managed to successfully evade capture on the ship.
Following this clash, the Night Lords legion scattered into various raiding parties. These groups would pillage and terrorize the Imperium for the remainder of the war, though at least some would join up with Horus in his drive on Terra.